Hobbies And Interests
Gas
Jupiter, Uranus, Saturn and Neptune are known as the Jovian planets due to their gaseous nature. They are the four planets furthest from the sun and have relatively low densities. The "Astronomy Cafe" suggests that these gigantic planets may have a small solid core. The planets are mostly composed of an outer layer of molecular helium and hydrogen, according to the "Sol Station" website, though Uranus and Neptune also feature liquids.
Solids
The four terrestrial planets are those closest to the sun, and all feature hard, rocky surfaces. Venus, Mercury, Earth and Mars developed from small particles of dust that collided and fused, eventually growing to their present size and density. The "Sol Station" website says that the surface of Mercury has about 350 different minerals while that of Mars has about 500. By comparison, Earth's surface has more than 4,400 known minerals.
Liquid
Earth is the only planet with liquid water on its surface in the solar system. The liquid contained within the planets on the outskirts of the solar system behaves strangely in the extreme conditions found there. According to the "Nature" website, the water inside Neptune and Uranus behaves neither as a straightforward solid or liquid. Instead, it may exist in a "superionic"' phase, in which oxygen atoms are frozen, but the hydrogen atoms are able to move around at high speed.
Dark Matter
Dark matter is invisible and poorly understood. According to NASA, scientists know more about what it is not than what it actually is. For example, they know it is not antimatter, black holes or dark clouds of normal matter. The "Universe Today" website cites research by scientists from the University of Arizona who suggest that dark matter attaches itself to the solar system through the gravitational pull of the sun and planets. Some planets therefore have more dark matter surrounding them than others. It remains to be seen what part dark matter plays in the overall composition of the solar system.